Emulsions, Treatment Fluids and Methods for Treating Subterranean Formations

ABSTRACT

Emulsions, treatment fluids and methods for treating subterranean formations are provided, wherein the emulsions comprise water, a water-immiscible liquid, one or more polymers, and an inverting surfactant composition comprising one or more surfactants selected from the group consisting of ethoxylated amine compounds, ethoxylated fatty acid compounds, and alkyl polyethyleneglycol ether carboxylic acid compounds, alkyl polyglycol ether carboxylic acid compounds, and salts or esters thereof. The emulsions are particularly suitable for use in brine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/382,347, filed Sep. 1, 2016.

FIELD OF THE ART

The present disclosure generally relates to emulsions, treatment fluidsand methods for treating subterranean formations.

BACKGROUND

In the drilling, completion, and stimulation of oil and gas wells, welltreatment fluids are often pumped into well bore holes under highpressure and at high flow rates causing the rock formation surroundingthe well bore to fracture. As the fluid is pumped through the pipe athigh flow rates (thousands of GPM) there is a significant amount offrictional resistance, which results in large energy requirements.

In order to reduce the friction between the well treatment fluid and thebore linings, friction pressure reducing additives have been combinedwith the treatment fluids and added during pumping so as to reduce pumppressure. For example, a type of well treatment commonly utilized forstimulating hydrocarbon production from a subterranean zone penetratedby a well bore is hydraulic fracturing. Hydraulic fracturing, alsoreferred to as fracing (or fracking), is used to initiate production inlow-permeability reservoirs and re-stimulate production in olderproducing wells. In hydraulic fracing, a fluid composition is injectedinto the well at pressures effective to cause fractures in thesurrounding rock formation. Fracing is used both to open up fracturesalready present in the formation and create new fractures.

Water soluble polymers can be used as friction reducers in welltreatment fluids to alter the rheological properties of the fluid sothat the turbulent flow is reduced, thereby preventing consequent energyloss in the fluid as it is pumped through the pipe. These types oftreatments are often called “slick water treatments or slick waterfracs.” In some instances, water soluble friction reducing polymers aresuspended in water in oil emulsions, wherein upon addition to theaqueous treatment fluid, the emulsion must invert to release thefriction reducing polymer into the fluid. Performance in the fielddepends (at least in part) upon the ability of the emulsions to invert,or break, quickly. Certain conditions, for example high brineconditions, can hinder the breaking of the emulsion. In particular, highbrines including potassium chloride, sodium chloride, seawater and otherAPI base brines that include barium, strontium, iron, calcium ormagnesium hardness can interfere with the inversion of emulsionpolymers.

BRIEF SUMMARY

Disclosed herein are emulsions comprising: water; a water-immiscibleliquid; greater than about 10% by weight one or more polymers; about0.1% to about 5% by weight of an inverting surfactant compositioncomprising one or more surfactants selected from the group consisting ofethoxylated amine compounds, ethoxylated fatty acid compounds, and alkylpolyethyleneglycol ether carboxylic acid compounds, alkyl polyglycolether carboxylic acid compounds, and salts or esters thereof.

Treatment fluids comprising the emulsions, as well as methods fortreating subterranean formations with the emulsions or treatment fluids,are also provided.

The disclosure may be understood more readily by reference to thefollowing detailed description of the various features of the disclosureand the examples included therein.

BRIEF DESCRIPTION OF FIGURES

FIGS. 1, 2 and 3 show the friction reduction profiles of samples ofcationic emulsion polyacrylamides with an exemplary inverting surfactantcomposition in three different brines.

FIGS. 4 and 5 show the friction reduction profiles of samples ofcationic emulsion polyacrylamides with a comparative invertingsurfactant (anionic or cationic) in three different brines.

FIG. 6 shows the friction reduction profiles of samples of cationicemulsion polyacrylamides with several exemplary inverting surfactantcompositions in brine.

FIG. 7 shows the friction reduction profiles of samples of anionicemulsion polyacrylamides with several exemplary inverting surfactantcompositions in brine.

DETAILED DESCRIPTION

The present disclosure provides aqueous treatment fluids and methods fortheir use in aqueous brines. The aqueous treatment fluids utilize anadvantageous combination of a water soluble polymer, which can beanionic, cationic, amphoteric or non-ionic, and an inverting surfactantcomposition which comprises one or more surfactants selected from thegroup consisting of ethoxylated amine compounds, ethoxylated fatty acidcompounds, and alkyl polyethyleneglycol ether carboxylic acid compounds,alkyl polyglycol ether carboxylic acid compounds, and salts or estersthereof.

The exemplary emulsions, treatment fluids and methods may be used toprovide rapid and enhanced friction reduction in aqueous brines, forexample in harsh brine conditions. The exemplary emulsions, treatmentfluids and methods may be used at a range of temperatures, even at lowtemperatures, without loss of polymer performance.

In exemplary embodiments, the emulsions, treatment fluids and methodscan be used to carry proppants into fractures, for example in fracturingapplications. High molecular weight polyacrylamides are commonly used infracturing applications as a friction reducer. Generally, crosslinkedfluids are used to carry proppants into the fractures, which typicallyrequires additional chemicals, such as crosslinkers, buffers andbreakers, to be incorporated into the fracturing fluid. In exemplaryembodiments, the emulsions and treatment fluid can be used to carryproppant while minimizing the use of other chemicals or additivestypically required by crosslinked fluids.

In slickwater fracturing, the water is made slick by adding frictionreducer. Slickwater frac fluids typically have low viscosities; a higherinjection flow rate can be used to carry proppant. The exemplaryemulsions, treatment fluids and methods can be used in slickwaterfracturing applications. Advantageously, the exemplary emulsions andtreatment fluids can be used in high brines with very fast inversion ofthe emulsion, very good friction reduction and with good proppantcarrying capabilities at higher loadings.

Polymers

As used herein, the terms “polymer,” “polymers,” “polymeric,” andsimilar terms are used in their ordinary sense as understood by oneskilled in the art, and thus may be used herein to refer to or describea large molecule (or group of such molecules) that contains recurringunits. Polymers may be formed in various ways, including by polymerizingmonomers and/or by chemically modifying one or more recurring units of aprecursor polymer. A polymer may be a “homopolymer” comprisingsubstantially identical recurring units formed by, e.g., polymerizing aparticular monomer. A polymer may also be a “copolymer” comprising twoor more different recurring units formed by, e.g., copolymerizing two ormore different monomers, and/or by chemically modifying one or morerecurring units of a precursor polymer. A polymer may also be a“terpolymer” which comprises three or more different recurring units.The term “polymer” as used herein is intended to include both the acidform of the polymer as well as its various salts.

In exemplary embodiments, the polymer is an emulsion polyacrylamide, forexample an emulsion polyacrylamide that can be used as afriction-reducing polymer. The term “friction reducing polymer” refersto a polymer that reduces energy losses due to friction between anaqueous fluid in turbulent flow and tubular goods, e.g. pipes, coiledtubing, and the like, and/or formation. The friction reducing polymer isnot intended to be limited to any particular type and may be syntheticpolymers, natural polymers, or viscoelastic surfactants. Suitablefriction reducing polymers are typically latex polymers or copolymers ofacrylamides, acrylates, guar gum, polyethylene oxide, and combinationsthereof. The friction reducing polymers may be anionic, cationic,amphoteric or non-ionic depending on desired application. In addition,various combinations can be used including but not limited tohydrophilic/hydrophobic combinations, functionalized natural and/orsynthetic blends of the above, or the like. In certain exemplaryembodiments, the friction reducing polymer is anionic. In certainexemplary embodiments, the friction reducing polymer is cationic. Incertain exemplary embodiments, the friction reducing polymer isnon-ionic. In certain exemplary embodiments, the friction reducingpolymer is amphoteric.

In exemplary embodiments, the polymer is a polymer useful in emulsioncompositions or an emulsion polymer.

In exemplary embodiments, the polymer is an emulsion polyacrylamide(EPAM). EPAMs are generally inverse emulsions (water-in-oil) in whichwater droplets containing the polymer are suspended in an oil phase.

In exemplary embodiments, the polymer is a polymer useful for enhancedoil recovery applications. The term “enhanced oil recovery” or “EOR”(also known as tertiary mineral oil production) refers to a process formineral oil production in which an aqueous injection fluid comprising atleast a water soluble polymer is injected into a mineral oil deposit.The techniques of tertiary mineral oil production include what is knownas “polymer flooding”. Polymer flooding involves injecting an aqueoussolution of a water-soluble thickening polymer through the injectionboreholes into the mineral oil deposit. As a result of the injection ofthe polymer solution, the mineral oil is forced through the cavities inthe formation, proceeding from the injection borehole, in the directionof the production borehole, and the mineral oil is produced through theproduction borehole. By virtue of the fact that the polymer formulationhas an increased viscosity as compared to the viscosity of water, therisk is reduced that the polymer formulation breaks through to theproduction borehole. It is thus possible to mobilize additional mineraloil in the formation. Details of polymer flooding and of polymerssuitable for this purpose are disclosed, for example, in “Petroleum,Enhanced Oil Recovery, Kirk-Othmer, Encyclopedia of Chemical Technology,online edition, John Wiley & Sons, 2010”. For polymer flooding, amultitude of different water-soluble thickening polymers have beenproposed, especially high molecular weight polyacrylamide, copolymers ofacrylamide and further comonomers, for example vinylsulfonic acid oracrylic acid. Polyacrylamide may be partly hydrolyzed polyacrylamide, inwhich some of the acrylamide units have been hydrolyzed to acrylic acid.It is known in the art to use inverse emulsions of polyacrylamide(co)polymers for enhanced oil recovery (EOR) in particular for use onoff-shore platforms. Such inverse emulsions typically comprise about 30wt. % of polymers. For use inverse emulsions are simply diluted withwater to the final concentration of the polymer.

In exemplary embodiments, the one or more polymers is water soluble. Inexemplary embodiments, the one or more polymers comprises anacrylamide-containing polymer. In exemplary embodiments, the one or morepolymers consists essentially of acrylamide-containing polymers. Inexemplary embodiments, the one or more polymers comprisespolyacrylamide, copolymers of acrylamide, sulfonated polyacrylamide,cationic polyacrylamide, anionic polyacrylamide, and partiallyhydrolyzed acrylamide. In exemplary embodiments, the one or morepolymers comprises acrylamide or partially hydrolyzed acrylamide and oneor more nonionic and/or anionic monomers.

Suitable non-ionic monomers include but are not limited to acrylamide,N-alkylacrylamides, N,N-dialkylacrylamides, methacrylamide,N-vinylmethylacetamide or formamide, vinyl acetate, vinyl pyrrolidone,alkyl methacrylates, acrylonitrile, N-vinylpyrrolidone other acrylic (orother ethylenically unsaturated) ester or other water insoluble vinylmonomers such as styrene or acrylonitrile.

The term “anionic monomer” refers to a monomer which possesses anegative charge. Representative anionic monomers include acrylic acid,sodium acrylate, ammonium acrylate, methacrylic acid,2-acrylamido-2-methylpropanesulfonic acid (AMPS), vinyl sulfonic acid,styrene sulfonic acid, maleic acid, sulfopropyl acrylate or methacrylateor other water-soluble forms of these or other polymerizable carboxylicor sulphonic acids, sulfomethylated acrylamide, allyl sulfonate,itaconic acid, acrylamidomethylbutanoic acid, fumaric acid,vinylphosphonic acid, allylphosphonic acid, phosphonomethylatedacrylamide, methacrylate, itaconate, 2-acrylamido 2-methyl propanesulphonate, sulfoalkyl(meth)acrylic acids, sulfonated styrenes,unsaturated dicarboxylic acids, sulfoalkyl(meth)acrylamides, vinylacetate, n-vinylformamide, n-vinylacetamide, n-vinylcaprolactam,n-vinylimidazole, n-vinylpyridine, n-vinylpyrolidone,acrylamidopropyltrimonium chloride, salts of said acids and the like, oranother anionic ethylenically unsaturated compound.

In a particular embodiment, the one or more polymers comprisesacrylamide or partially hydrolyzed acrylamide and one or more anionicmonomers. In exemplary embodiments, the one or more polymers has anoverall anionic charge and comprises acrylamide or partially hydrolyzedacrylamide and one or more nonionic and/or anionic monomers. Inexemplary embodiments, the one or more polymers comprises about 5% toabout 60% anionic monomers by weight. In exemplary embodiments, the oneor more polymers comprises an anionic polyacrylamide. In exemplaryembodiments, the anionic polyacrylamide is a copolymer comprising one ormore anionic monomers and acrylamide monomers. Exemplary salts of theseanionic monomers include but are not limited to sodium and ammoniumsalts. In one embodiment, the polymer is an anionic polymer. In aparticular embodiment, the anionic polymer has about 5% to about 60%charge, about 10% to about 50% charge, about 15% to about 45% charge,about 20% to about 40% charge, about 10% to about 15% charge, or about25% to about 35% charge.

In exemplary embodiments, the one or more polymers comprises acrylamideor partially hydrolyzed acrylamide and one or more cationic monomers.

The term “cationic monomer” refers to a monomer which possesses apositive charge. Representative cationic monomers includedialkylaminoalkyl acrylates and methacrylates and their quaternary oracid salts, including, but not limited to, dimethylaminoethyl acrylatemethyl chloride quaternary salt, dimethylaminoethyl acrylate methylsulfate quaternary salt, dimethyaminoethyl acrylate benzyl chloridequaternary salt, dimethylaminoethyl acrylate sulfuric acid salt,dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethylacrylate, methyl chloride quaternary salt, dimethylaminoethylmethacrylate methyl chloride quaternary salt, dimethylaminoethylmethacrylate methyl sulfate quaternary salt, dimethylaminoethylmethacrylate benzyl chloride quaternary salt, dimethylaminoethylmethacrylate sulfuric acid salt, dimethylaminoethyl methacrylatehydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloricacid salt, dialkylaminoalkylacrylamides or methacrylamides and theirquaternary or acid salts such as acrylamidopropyltrimethylammoniumchloride, dimethylaminopropyl acrylamide methyl sulfate quaternary salt,dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropylacrylamide hydrochloric acid salt, methacrylamidopropyltrimethylammoniumchloride, dimethylaminopropyl methacrylamide methyl sulfate quaternarysalt, dimethylaminopropyl methacrylamide sulfuric acid salt,dimethylaminopropyl methacrylamide hydrochloric acid salt,acryloyloxyethyltrimethylammonium chloride, diethylaminoethylacrylate,diethylaminoethylmethacrylate and diallyldialkylammonium halides such asdiallyldiethylammonium chloride and diallyldimethyl ammonium chloride.Alkyl groups are generally C₁₋₈ alkyl.

In a particular embodiment, the one or more polymers comprisesacrylamide or partially hydrolyzed acrylamide and one or more cationicmonomers. In a particular embodiment, the one or more polymers comprisesacrylamide or partially hydrolyzed acrylamide andacryloyloxyethyltrimethylammonium chloride. In exemplary embodiments,the one or more polymers has an overall cationic charge and comprisesacrylamide or partially hydrolyzed acrylamide and one or more cationicmonomers. In exemplary embodiments, the one or more polymers comprisesabout 5% to about 60% cationic monomers by weight. In exemplaryembodiments, the one or more polymers comprises a cationicpolyacrylamide. In exemplary embodiments, the cationic polyacrylamide isa copolymer comprising one or more cationic monomers and acrylamidemonomers. In one embodiment, the polymer is a cationic polymer.

In exemplary embodiments, the partially hydrolyzed acrylamide isacrylamide wherein about 3% to about 70% of the amide groups have beenhydrolyzed to carboxyl groups.

In one embodiment, the one or more polymers comprises an amphotericpolymer. In one embodiment, the one or more polymers comprises anon-ionic polymer.

In exemplary embodiments, the one or more polymers comprises acrylamideor partially hydrolyzed acrylamide and one or more monomers selectedfrom the group consisting of acrylic acid, acrylate salt,2-acrylamido-2-methylpropane sulfonic acid, N,N-dimethylacrylamide,vinyl sulfonic acid, N-vinyl sulfonic acetamide, N-vinyl formamide,itaconic acid, methacrylic acid, acryloyloxyethyltrimethylammoniumchloride, salts thereof, and combinations thereof. In a particularembodiment, the one or more polymers comprises acrylamide or partiallyhydrolyzed acrylamide and one or more monomers selected from the groupconsisting of acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid,and methacrylic acid, and salts thereof. In a particular embodiment, theone or more polymers comprises acrylamide or partially hydrolyzedacrylamide and one or more monomers selected from the group consistingof acrylic acid and salts thereof.

In certain embodiments, the polymer comprises acrylamide and one or moremonomers selected from the group consisting of: acrylic acid and itssalts, methacrylamide, methacrylic acid and its salts, maleic acid andits salts, methyl acrylate, ethyl acrylate, propyl acrylate, methylmethacrylate, ethyl methacrylate, dimethylaminoethyl acrylate and itsmethylchloride and methosulfate quaternaries, dimethylaminoethylmethacrylate and its methylchloride and methosulfate quaternaries,diethylaminoethyl acrylate and its methylchloride and methosulfatequaternaries, diethylaminoethyl methacrylate and its methylchloride andmethosulfate quaternaries, hydroxyethyl acrylate, hydroxyethylmethacrylate, styrene, acrylonitrile, 2-acrylamido-2-methylpropanesulfonic acid and its salts,3-(methylacrylamido)-propyltrimethylammonium chloride,dimethylaminopropylmethacrylamide, isopropylaminopropylmethacrylamide,methacrylamidopropylhydroxyethyldimethylammonium acetate, vinyl methylether, vinyl ethyl ether, alkali metal and ammonium salts of vinylsulfonic acid, vinyl pyridine, vinyl pyrrolidone, vinyl imidazole,diallyldimethylammonium chloride, styrene sulfonic acid and its salts,and the like.

In exemplary embodiments, one or more polymers is a copolymer ofacrylamide or partially hydrolyzed acrylamide and one or more anionicmonomers. In exemplary embodiments, the one or more polymers comprisesat least about 40 mole %, about 50 mole %, about mole 60%, about mole70%, about mole 80%, or about mole 90% acrylamide or partiallyhydrolyzed acrylamide. In exemplary embodiments, the one or morepolymers comprises at least about 5 mole %, about 10 mole %, about 20mole %, about 30 mole %, about 40 mole %, about 50 mole %, or about 55mole % one or more anionic monomers. In exemplary embodiments, the oneor more polymers comprises about 40 mole % to about 95 mole %, or about60 mole % to about 90 mole %, acrylamide or partially hydrolyzedacrylamide. In exemplary embodiments, the one or more polymers comprisesabout 5 mole % to about 60 mole %, or about 10 mole % to about 40 mole%, one or more anionic monomers.

In exemplary embodiments, one or more polymers is a copolymer ofacrylamide or partially hydrolyzed acrylamide and one or more cationicmonomers. In exemplary embodiments, the one or more polymers comprisesat least about 40 mole %, about 50 mole %, about mole 60%, about mole70%, about mole 80%, or about mole 90% acrylamide or partiallyhydrolyzed acrylamide. In exemplary embodiments, the one or morepolymers comprises at least about 5 mole %, about 10 mole %, about 20mole %, about 30 mole %, about 40 mole %, about 50 mole %, or about 55mole % one or more cationic monomers. In exemplary embodiments, the oneor more polymers comprises about 40 mole % to about 95 mole %, or about60 mole % to about 90 mole %, acrylamide or partially hydrolyzedacrylamide. In exemplary embodiments, the one or more polymers comprisesabout 5 mole % to about 60 mole %, or about 10 mole % to about 40 mole%, one or more cationic monomers.

In exemplary embodiments, one or more polymers is a copolymer ofacrylamide or partially hydrolyzed acrylamide and acrylic acid or anacrylate salt. In exemplary embodiments, the one or more polymerscomprises at least about 40 mole %, about 50 mole %, about mole 60%,about mole 70%, about mole 80%, or about mole 90% acrylamide orpartially hydrolyzed acrylamide. In exemplary embodiments, the one ormore polymers comprises at least about 5 mole %, about 10 mole %, about20 mole %, about 30 mole %, about 40 mole %, about 50 mole %, or about55 mole % acrylic acid or acrylate salts. In exemplary embodiments, theacrylate salt comprises ammonium acrylate. In exemplary embodiments, theone or more polymers comprises about 40 mole % to about 95 mole %, orabout 60 mole % to about 90 mole %, acrylamide or partially hydrolyzedacrylamide. In exemplary embodiments, the one or more polymers comprisesabout 5 mole % to about 60 mole %, or about 10 mole % to about 40 mole%, acrylic acid or an acrylate salt.

The exemplary polymers may be included in the treatment fluids in anamount sufficient to provide the desired properties. In someembodiments, a polymer may be present in an amount in the range of about0.1 to about 10, about 0.1 to about 6, about 0.1 to about 5, or about0.25 to about 1, Gallons Per Thousand Gallons of the aqueous treatmentfluid (GPTG). The polymers may be added to slick water treatments atconcentrations of about 0.1 to about 20 GPTG, of treatment fluid. Inother embodiments, the polymer is added at a concentration of about 0.25to about 6 GPTG of treatment fluid.

The polymers of the present embodiments should have a molecular weightsufficient to provide desired properties. For example, those polymersused for friction reduction should have higher molecular weights toprovide a desirable level of friction reduction. The polymers used forEOR applications should have sufficient molecular weight to provide thedesired viscosity to mobilize oil in a desirable manner. In someexemplary embodiments, the weight average molecular weight of a polymermay be in the range of from about 7,500,000 to about 30,000,000 Dalton.Those of ordinary skill in the art will recognize that polymers havingmolecular weights outside the listed range may still provide desirableproperties in the aqueous treatment fluid.

In exemplary embodiments, the polymer is used for EOR applications.

Suitable polymers of the present embodiments may be in an acid form orin a salt form. A variety of salts may be made by neutralizing the acidform of a monomer, for example acrylic acid or2-acrylamido-2-methylpropane sulfonic acid, with a base, such as sodiumhydroxide, ammonium hydroxide or the like. As used herein, the term“polymer” is intended to include both the acid form of the copolymer andits various salts.

Inverting Surfactant Composition

In exemplary embodiments, in addition to the one or more polymers, theemulsion or aqueous treatment fluid comprises an inverting surfactantcomposition. Among other things, an inverting surfactant or invertingsurfactant composition may facilitate the inverting of the emulsion uponaddition to the treatment fluids of the present embodiments. As those ofordinary skill in the art will appreciate, with the benefit of thisdisclosure, upon addition to the treatment fluid, the emulsion shouldinvert, releasing the polymer into the treatment fluid.

In exemplary embodiments, the inverting surfactant composition comprisesone or more surfactants selected from the group consisting of SurfactantA compounds, Surfactant B compounds, and Surfactant C compounds, asdescribed herein. In certain exemplary embodiments, the invertingsurfactant composition comprises one or more surfactants selected fromthe group consisting of Surfactant A compounds. In certain exemplaryembodiments, the inverting surfactant composition comprises one or moresurfactants selected from the group consisting of Surfactant Bcompounds.

In exemplary embodiments, the inverting surfactant composition comprisestwo or more surfactants selected from the group consisting of SurfactantA compounds, Surfactant B compounds, and Surfactant C compounds, asdescribed herein.

In exemplary embodiments, the inverting surfactant composition comprisesone or more Surfactant A compounds. In exemplary embodiments, theinverting surfactant composition comprises one or more Surfactant Bcompounds. In exemplary embodiments, the inverting surfactantcomposition comprises one or more Surfactant C compounds.

In exemplary embodiments, the inverting surfactant composition comprisesone or more Surfactant A compounds and one or more Surfactant Bcompounds. In exemplary embodiments, the inverting surfactantcomposition comprises one or more Surfactant A compounds and one or moreSurfactant C compounds. In exemplary embodiments, the invertingsurfactant composition comprises one or more Surfactant B compounds andone or more Surfactant C compounds. In exemplary embodiments, theinverting surfactant composition comprises two or more types ofSurfactant B compounds.

In exemplary embodiments, the inverting surfactant composition comprisesone or more Surfactant A compounds, one or more Surfactant B compounds,and one or more Surfactant C compounds. In exemplary embodiments, theinverting surfactant composition comprises one or more Surfactant Acompounds, two or more types of Surfactant B compounds. In exemplaryembodiments, the inverting surfactant composition comprises one or moreSurfactant C compounds, two or more types of Surfactant B compounds.

In exemplary embodiments, the inverting surfactant composition comprisesone or more Surfactant A compounds, two or more types of Surfactant Bcompounds, one or more Surfactant C compounds.

In exemplary embodiments, the inverting surfactant composition maycomprise other inverting surfactants in addition to those chosen fromSurfactant A, Surfactant B, and Surfactant C compounds. Representativeinverting surfactants that may also be added to the exemplary emulsionsinclude those having a hydrophilic-lipophilic balance (HLB) of greaterthan 10; polyoxyethylene sorbitol tetraoleate; polyethylene glycolmonoleate; ethoxylated alcohols, such as C₁₂₋₁₄ branched ethoxylatedalcohol, ethoxylated octyl and nonyl phenols; ethoxylated nonyl phenolformaldehyde resin; polyethylene oxide esters of fatty acids; dioctylesters of sodium sulfosuccinate; and other inverting surfactantsdisclosed in U.S. Pat. No. 3,624,019 incorporated herein by reference.The inverting surfactant should be present in an amount sufficient toprovide the desired inversion of the emulsion upon contact with thewater in the aqueous treatment fluid.

In exemplary embodiments, the inverting surfactant composition comprises0 to about 100%, 0 to about 75%, or about 5 to about 75 wt %, ofSurfactant A compounds. In exemplary embodiments, the invertingsurfactant composition comprises at least about 5, about 10, about 15,about 20, about 25, about 30, about 35, about 40, about 50, about 55,about 60, about 65, about 70, about 75, about 80, about 85, about 90, orabout 95 wt % of Surfactant A compounds, when Surfactant A is includedin the composition. In certain exemplary embodiments, the invertingsurfactant composition does not comprise Surfactant A compounds.

In exemplary embodiments, the inverting surfactant composition comprises0 to about 100%, 0 to about 75%, or about 5 to about 75 wt %, ofSurfactant B compounds. In exemplary embodiments, the invertingsurfactant composition comprises at least about 5, about 10, about 15,about 20, about 25, about 30, about 35, about 40, about 50, about 55,about 60, about 65, about 70, about 75, about 80, about 85, about 90, orabout 95 wt % of Surfactant B compounds, when Surfactant B is includedin the composition. In certain exemplary embodiments, the invertingsurfactant composition does not comprise Surfactant B compounds.

In exemplary embodiments, the inverting surfactant composition comprises0 to about 75%, or about 5 to about 50 wt %, of Surfactant C compounds.In exemplary embodiments, the inverting surfactant composition comprisesat least about 5, about 10, about 15, about 20, about 25, about 30,about 35, about 40, or about 50 wt % of Surfactant C compounds, whenSurfactant C is included in the composition. In certain exemplaryembodiments, the inverting surfactant composition does not compriseSurfactant C compounds.

In certain exemplary embodiments, the inverting surfactant compositioncomprises or consists essentially of about 5 to about 95 wt % one ormore Surfactant A compounds and about 5 to about 95 wt % one or moreSurfactant B compounds. In certain exemplary embodiments, the invertingsurfactant composition comprises or consists essentially of about 25 toabout 35 wt % one or more Surfactant A compounds and about 65 to about75 wt % one or more Surfactant B compounds.

In certain exemplary embodiments, the inverting surfactant compositioncomprises or consists essentially of about 5 to about 95 wt % one ormore Surfactant A compounds and about 5 to about 75 wt % one or moreSurfactant C compounds. In certain exemplary embodiments, the invertingsurfactant composition comprises or consists essentially of about 5 toabout 95 wt % one or more Surfactant B compounds and about 5 to about 75wt % one or more Surfactant C compounds. In certain exemplaryembodiments, the inverting surfactant composition comprises or consistsessentially of about 25 to about 65, about 25 to about 55, about 30 toabout 50, or about 30 to about 60, wt % one or more Surfactant Bcompounds and about 35 to about 75, about 45 to about 75, about 40 toabout 70, about 50 to about 70 wt % one or more Surfactant C compounds.

In certain exemplary embodiments, the inverting surfactant compositioncomprises or consists essentially of about 5 to about 95 wt % one ormore Surfactant B compounds and about 5 to about 95 wt % a differentSurfactant B compound.

In certain exemplary embodiments, the inverting surfactant compositioncomprises or consists essentially of about 5 to about 90 wt % one ormore Surfactant A compounds, about 5 to about 90 wt % one or moreSurfactant B compounds and about 5 to about 75 wt % one or moreSurfactant C compounds. In certain exemplary embodiments, the invertingsurfactant composition comprises or consists essentially of about 5 toabout 35, or about 10 to about 30, wt % one or more Surfactant Acompounds; about 25 to about 70, or about 30 to about 60, wt % one ormore Surfactant B compounds; and about 15 to about 70, about 15 to about55, about 20 to about 50, about 35 to about 65, or about 40 to about 60,wt % one or more Surfactant C compounds. In certain exemplaryembodiments, the inverting surfactant composition comprises or consistsessentially of about 15 to about 35, about 25 to to about 35, about 20to about 30, about 15 to about 25, or about 5 to about 15, wt % one ormore Surfactant A compounds; about 15 to about 45, about 35 to about 45;about 45 to about 55, about 55 to about 65, about 65 to about 75, orabout 20 to about 40, wt % one or more Surfactant B compounds; and about15 to about 65, about 15 to about 25, about 25 to about 35, about 35 toabout 45, about 45 to about 55, about 55 to about 65, or about 30 toabout 50, wt % one or more Surfactant C compounds.

In certain exemplary embodiments, the inverting surfactant compositioncomprises or consists essentially of about 5 to about 75 wt % one ormore Surfactant A compounds, about 5 to about 75 wt % two or more typesof Surfactant B compounds, and about 5 to about 75 wt % one or moreSurfactant C compounds. In a particular embodiment, the invertingsurfactant composition comprises or consists essentially of about 25 toabout 35, or about 28 to about 32, wt % one or more Surfactant Acompounds, about 25 to about 35, or about 28 to about 32, wt % one ormore Surfactant B compounds, about 25 to about 35, or about 28 to about32, wt % one or more Surfactant C compounds and about 5 to about 15, orabout 8 to about 12, wt % of a different Surfactant B compound.

Surfactant A

In exemplary embodiments, the emulsion or aqueous treatment fluidcomprises one or more Surfactant A compounds. In exemplary embodiments,Surfactant A compounds are selected from ethoxylated amine compounds,such as ethoxylated tallow amine compounds. As referred to herein,“ethoxylated amine compounds” includes, for example, amine or amidecompounds comprising two ethoxy or polyethoxy groups and one groupselected from hydrogen, alkyl, aryl, C(═O)-alkyl or C(═O)-aryl group. Incertain exemplary embodiments, the ethoxylated amine compounds arenonionic amine compounds. In certain embodiments, the ethoxylated aminecompounds do not comprise cationic polyoxyethylene tallow aminecompounds.

In exemplary embodiments the ethoxylated amine compounds are compoundsof Formula I:

wherein R¹ is H, alkyl, aryl, C(═O)-alkyl, or C(═O)-aryl; and X and Yare each independently 1-20. In exemplary embodiments, an alkyl group isa saturated or unsaturated alkyl group having 8 to 26 carbon atoms. Inexemplary embodiments, an aryl group is an aryl group having 6 to 18carbon atoms. In exemplary embodiments, the alkyl group can be eithersaturated or unsaturated, and can be derived from, but not limited to,tallow, soybean oil, coconut oil, or cottonseed oil. In exemplaryembodiments, the poly(oxyethylene) content (X+Y) of the ethoxylatedamine is in the range of 3 to 20.

In certain embodiments, R¹ is H. In certain embodiments, R¹ is not H. Incertain embodiments, R¹ is alkyl, for example is a saturated orunsaturated alkyl group having 8 to 26 carbon atoms. In certainembodiments, le is C(═O)-alkyl, for example a carbonyl group bonded tothe amine nitrogen and to a saturated or unsaturated alkyl group having8 to 26 carbon atoms, such as N,N-bis(2-hydroxyethyl)-9-octadecenamide.

It should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1-10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10. Because the disclosed numerical ranges are continuous, theyinclude every value between the minimum and maximum values.

In exemplary embodiments, the ethoxylated amine compounds ispolyethylene fatty acid amine or a mixture of polyethylene fatty acidamine compounds.

In exemplary embodiments, R¹ is a residue of a saturated or unsaturatedfatty acid, for example a residue of caprylic acid, capric acid, lauricacid, myristic acid, palmitic acid, stearic acid, arachidic acid,behenic acid, lignoceric acid, cerotic acid, myristoleic acid,palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenicacid, linoleic acid, linoelaidic acid, α-linolenic acid, arachidonicacid, eicosapentaenoic acid, erucic acid, or docosahaxaenoic acid.

In exemplary embodiments, the one or more ethoxylated amine compounds ispolyethylene tallow amine. Tallow contains a variety of fatty acidsincluding oleic (37-43%), palmitic (24-32%), stearic (20-25%), myristic(3-6%) and linoleic (2-3%). In exemplary embodiments, the one or moreethoxylated amine compounds includes polyethylene oleic amine,polyethylene palmitic amine, polyethylene stearic amine, polyethylenemyristic amine, and polyethylene linoleic amine.

Surfactant B

In exemplary embodiments, the emulsion or aqueous treatment fluidcomprises one or more Surfactant B compounds. In exemplary embodiments,Surfactant B compounds are selected from alkyl polyethyleneglycol ethercarboxylic acid compounds, alkyl polyglycol ether carboxylic acidcompounds, and salts or esters thereof. As referred to herein,Surfactant B compounds include, for example, compounds comprising a C₈to C₂₆ unsaturated or saturated alkyl chain substituted with an(OCH₂CH₂)_(y)OCH₂CO₂H wherein the average value of y is about 2 to about20, or about 2 to about 10. In certain exemplary embodiments, the alkylpolyglycol ether carboxylic acid compounds are anionic compounds.

In exemplary embodiments, Surfactant B compounds comprise a C₁₄ to C₂₂unsaturated alkyl chain, for example an unsaturated alkyl chain derivedfrom a fatty acid residue, such as oleic acid, myristoleic acid,palmitoleic acid, sapienic acid, elaidic acid, vaccenic acid, linoleicacid, α-linoleic acid, linoelaidic, arachidonic acid, eicospentanoicacid, erucic acid, docosahexaenoic acid, and the like. In exemplaryembodiments, the Surfactant B is selected from the group consisting ofglycolic acid ethoxylate oleyl ether, glycolic acid ethoxylatemyristoleyl ether, glycolic acid ethoxylate palmitoleyl ether, glycolicacid ethoxylate sapienyl ether, glycolic acid ethoxylate elaidyl ether,glycolic acid ethoxylate vaccenyl ether, glycolic acid ethoxylatedlinoleyl ether, glycolic acid ethoxylated a-linoleyl ether, glycolicacid ethoxylate linoelaidyl ether, glycolic acid ethoxylate arachidonylether, glycolic acid ethoxylate eicospentanoyl ether, glycolic acidethoxylate erucyl ether, and glycolic acid ethoxylated docosahexaenoylether.

In certain exemplary embodiments, Surfactant B is a compound or amixture of compounds represented by the formula:CH₃(CH₂)_(x)CH═CH(CH₂)₈(OCH₂CH₂)_(y)OCH₂CO₂H, wherein x is 1-12 and y is2-20.

In certain exemplary embodiments, the Surfactant B is glycolic acidethoxylate oleyl ether. In certain exemplary embodiments, Surfactant Bis the mixture of compounds represented by the formula:CH₃(CH₂)_(x)CH═CH(CH₂)₈(OCH₂CH₂)_(y)OCH₂CO₂H, wherein the average valuefor x is 5-7 and the average value for y is about 2. In exemplaryembodiments, Surfactant B compounds comprise a C₁₄ to C₂₂ saturatedalkyl chain, for example an saturated alkyl chain derived from a fattyacid residue, such as caprylic acid, capric acid, lauric acid, myristicacid, palmitic acid, stearic acid, arachidic acid, behenic acid,lignoceric acid, cerotic acid, and the like. In exemplary embodiments,the Surfactant B is selected from the group consisting of glycolic acidethoxylate lauryl ether, glycolic acid ethoxylate caprylyl ether,glycolic acid ethoxylate capryl ether, glycolic acid ethoxylate myristylether, glycolic acid ethoxylate palmityl ether, glycolic acid ethoxylatestearyl ether, glycolic acid ethoxylated arachidyl ether, glycolic acidethoxylated behenyl ether, glycolic acid ethoxylate lignoceryl ether,and glycolic acid ethoxylate cerotyl ether.

In certain exemplary embodiments, Surfactant B is a compound or amixture of compounds represented by the formula:CH₃(CH₂)_(w)(OCH₂CH₂)_(y)OCH₂CO₂H, wherein w is 6-24 and y is 2-20.

In certain exemplary embodiments, the Surfactant B is a glycolic acidethoxylate lauryl ether or a polyoxyethylene lauryl ether carboxylicacid or a salt thereof, such as polyoxyethylene(10) lauryl ethercarboxylic acid, polyoxyethylene(3) lauryl ether carboxylic acid,polyoxyethylene(5) lauryl ether carboxylic acid, polyoxyethylene(7)lauryl ether carboxylic acid, or polyoxyethylene(4) lauryl ethercarboxylic acid.

In certain exemplary embodiments, the Surfactant B is B1 or B2 from theExamples, or a combination thereof.

Surfactant C

In exemplary embodiments, the emulsion or aqueous treatment fluidcomprises one or more Surfactant C compounds. In exemplary embodiments,Surfactant C compounds are selected from ethoxylated fatty acidcompounds. As referred to herein, “ethoxylated fatty acid compounds”includes, for example, fatty acid compounds which have been reacted withethylene oxide to form compounds containing at least 20 moles of ethoxygroups per 1 mole of the fatty acid. In certain exemplary embodiments,the ethoxylated fatty acid compounds are unsaturated, for examplemonounsaturated. In certain exemplary embodiments, the ethoxylated fattyacid compounds are hydroxylated or substituted with one or more hydroxylgroups. In certain exemplary embodiments, the ethoxylated fatty acidcompounds are nonionic compounds. In exemplary embodiments, Surfactant Ccompound contains at least about 20, about 25, about 30, or about 35units of ethoxylation.

In certain exemplary embodiments, the fatty acid is, for example, amonounsaturated hydroxyl fatty acid, such as Ricinoleic acid. Ricinoleicacid (12-hydroxy-9-cis-octadecenoic acid) is an unsaturated omega-9fatty acid and a hydroxy acid. It is a major component of the seed oilobtained from mature Castor plant (Ricinus communis L., Euphorbiaceae)seeds or in sclerotium of ergot (Claviceps purpurea Tul.,Clavicipitaceae). About 90% of the fatty acid content in castor oil isthe triglyceride formed from ricinoleic acid.

In certain exemplary embodiments, Surfactant C is ethoxylated castoroil.

In exemplary embodiments, the Surfactant C compound is produced by theethoxylation of fatty acid materials derived from saturated orunsaturated animal or vegetable fats, such as coconut oil, tall oil,stearic fatty acid, oleic fatty acid or adipic fatty acid.

In certain exemplary embodiments, the ethoxylated fatty acid compoundis, for example, coconut fatty acid ethoxylate, lauric acid ethoxylate,oleic acid ethoxylate, or myristic acid ethoxylate.

Emulsions

Exemplary emulsions, for example water-in-oil emulsions or oil-externalemulsions, may comprise water, a water-immiscible liquid, one or morepolymers, and an inverting surfactant composition comprising one or moresurfactants selected from the group consisting of Surfactant Acompounds, Surfactant B compounds, and Surfactant C compounds, asdescribed herein. In certain exemplary embodiments, the emulsionscomprise water, a water-immiscible liquid, one or more polymers, and aninverting surfactant composition comprising one or more Surfactant Acompounds. In certain exemplary embodiments, the emulsions comprisewater, a water-immiscible liquid, one or more polymers, and an invertingsurfactant composition comprising one or more Surfactant B compounds. Incertain exemplary embodiments, the emulsions comprise water, awater-immiscible liquid, one or more polymers, and an invertingsurfactant composition comprising one or more Surfactant C compounds. Incertain exemplary embodiments, the emulsions comprise water, awater-immiscible liquid, one or more polymers, and an invertingsurfactant composition comprising two or more surfactants selected fromthe group consisting of Surfactant A compounds, Surfactant B compounds,and Surfactant C compounds. In certain exemplary embodiments, theemulsions comprise water, a water-immiscible liquid, one or morepolymers, and an inverting surfactant composition comprising three ormore surfactants selected from the group consisting of Surfactant Acompounds, Surfactant B compounds, and Surfactant C compounds. Incertain exemplary embodiments, the emulsions comprise water, awater-immiscible liquid, one or more polymers, and an invertingsurfactant composition comprising four or more surfactants selected fromthe group consisting of Surfactant A compounds, Surfactant B compounds,and Surfactant C compounds. The emulsion may optionally compriseinhibitors, emulsifiers, salts and/or other surfactants.

In exemplary embodiments, the emulsion comprises: water; awater-immiscible liquid; greater than about 10% by weight one or morepolymers; about 0.1% to about 5% by weight an inverting surfactantcomposition described herein. In exemplary embodiments, the emulsioncomprises: water; a water-immiscible liquid; greater than about 10% byweight one or more polymers; about 0.1% to about 5%, about 1% to about4%, or about 1.5% to about 3.5%, by weight an inverting surfactantcomposition comprising one or more surfactants selected from the groupconsisting of Surfactant A compounds, Surfactant B compounds, andSurfactant C compounds. In exemplary embodiments, the amounts of eachindividual inverting surfactant included in the emulsion, when two ormore exemplary inverting surfactants are used can vary as necessary, forexample, each exemplary inverting surfactant can be present in an amountof about 0.01 to about 5%, 0.01 to about 3%, or about 0.02 to about 2%,by weight, based on the total emulsion.

The water present in the emulsions generally includes freshwater, butsaltwater or combinations with saltwater also may be used. Generally,the water used may be from any source, provided that it does not containan excess of compounds that may adversely affect other components in theemulsion. In some embodiments, the water may be present in the emulsionin an amount in the range of from about 1% to about 50%, about 1% toabout 12%, about 3% to about 50%, about 3% to about 12%, about 1% toabout 5%, about 12% to about 50%, or about 30% to about 50% by weight ofthe emulsion. In some embodiments, the emulsion composition may haveless than about 30%, about 20%, about 12%, about 10%, about 7%, about5%, or about 3% by weight water. In some embodiments, the emulsioncomposition may have greater than about 1%, about 2%, about 3%, about5%, about 7%, about 10%, about 12%, or about 20%, by weight water. Incertain exemplary embodiments, the emulsion can be water-free or atleast substantially water-free. In embodiments wherein the amount ofwater in the emulsion is kept to a very small amount, the emulsion maybe in the form of a liquid dispersion polymer composition or a liquidpolymer composition.

Suitable water-immiscible liquids may include, but are not limited to,water-immiscible solvents, such as paraffin hydrocarbons, naphthenehydrocarbons, aromatic hydrocarbons, olefins, oils, stabilizingsurfactants and mixtures thereof. The paraffin hydrocarbons may besaturated, linear, or branched paraffin hydrocarbons. Examples ofsuitable aromatic hydrocarbons include, but are not limited to, tolueneand xylene. In one embodiment, the water-immiscible liquid is an olefinand paraffin blend. In one embodiment, the water-immiscible liquidcomprises oil and one or more emulsifiers. The water-immiscible liquidmay be present in the emulsion in an amount sufficient to form a stableemulsion. In some embodiments, the water-immiscible liquid may bepresent in the emulsions in an amount in the range of from about 20% toabout 60%, about 25% to about 55%, about 35% to about 55%, or about 20%to about 30% by weight.

In exemplary embodiments, the emulsion comprises one or moreemulsifiers. Emulsifiers, among other things, in the emulsion, lower theinterfacial tension between the water and the water-immiscible liquid soas to facilitate the formation of a water-in-oil polymer emulsion. Inexemplary embodiments, the emulsifier is not a compound of SurfactantsA, B, or C. The emulsifier should be present in an amount sufficient toprovide the desired stable water-in-oil polymer emulsion. In someembodiments, the emulsifier may be present in an amount in the range offrom about 0.5% to about 5% by weight of the emulsion.

The polymer should be present in the emulsion in an amount that does notundesirably impact the emulsion's stability. In exemplary embodiments,the one or more polymers may be present in an amount in the range offrom about 10% to about 80%, about 10% to about 35%, about 15% to about30%, or about 20% to about 30%, about 39% to about 80%, or about 40% toabout 60%, or about 45% to about 55%, by weight of the emulsion. Inexemplary embodiments, the emulsion may comprise greater than about 35%,about 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%,52%, 53%, 54%, 55%, 56%, 57%, 58%, 59% or about 60% or higher, by weightpolymer. In exemplary embodiments, the emulsion may comprise less thanabout 35%, or about 30%, or less, by weight polymer.

In certain exemplary embodiments, the emulsions may further comprise oneor more organic or inorganic salts. In certain exemplary embodiments,the emulsions comprise at least about 0.5% of one or more organic orinorganic salts. In exemplary embodiments, the emulsions comprise one ormore organic or inorganic salts in an amount about 0.5% to about thepoint of saturation in the emulsion. Representative organic or inorganicsalts include but are not limited to sodium chloride, sodium sulfate,sodium bromide, ammonium sulfate, ammonium chloride, lithium chloride,lithium bromide, potassium chloride, potassium bromide, magnesiumsulfate, aluminum sulfate, ammonium hydrogen phosphate, sodium hydrogenphosphate, potassium hydrogen phosphate, sodium salts, lithium salts,potassium salts, magnesium salts, aluminum salts, ammonium salts,phosphate salts, sulfate salts, chloride salts, fluoride salts, citratesalts, acetate salts, tartrate salts, hydrogenphosphate salts, watersoluble inorganic salts, other inorganic salts, other organic salts andmixtures thereof In exemplary embodiments, the one or more organic orinorganic salts includes ammonium chloride.

In some embodiments, emulsion polymerization may be used to prepareexemplary emulsions. Suitable emulsion polymerization techniques mayhave a variety of different initiation temperatures depending on, amongother things, the amount and type of initiator used, the amount and typeof monomers used, and a number of other factors known to those ofordinary skill in the art. In one embodiment, a suitable emulsionpolymerization technique may have an initiation temperature of about 25°C. Due to the exothermic nature of the polymerization reaction, themixture may be maintained at a higher temperature than the initiationtemperature during procession of the polymerization reaction, forexample, in the range of from about 30° C. to about 70° C., or fromabout 40° C. to about 60° C.

In exemplary embodiments, the one or more polymers are in the form of aemulsion, such as a polyacrylamide emulsion. In exemplary embodiments,the emulsion comprises a hydrophilic polymer contained within waterdroplets that are dispersed in a continuous oil phase. In exemplaryembodiments, the one or more polymers are in the form of an aqueousdispersion, for example an aqueous polymer dispersion prepared bysolution polymerization. Methods for the preparation of exemplaryaqueous polymer dispersions are well known in the art, for example asdescribed in U.S. Pat. No. 5,200,448.

In exemplary embodiments, any suitable emulsion polymerization methodmay be employed in the preparation of the one or more polymers describedhere. Descriptions of the steps of an exemplary emulsion preparationprovided herein, but are not intended to be limiting with respect to themethods for preparing the exemplary one or more polymers.

A preliminary emulsion is made by homogenizing oil and aqueous phases.The oil phase of the emulsion, which generally comprises from about 5 toabout 35 percent by weight of the total emulsion, is comprised of one ormore inert hydrophobic liquids. Preferably, the oil phase comprisesabout 20 to 30 percent of the emulsion. The oil used may be selectedfrom a large class of organic liquids which are immiscible with water,including liquid hydrocarbons and substituted liquid hydrocarbons.Representative examples of such oils include benzene, xylene, toluene,mineral oils, kerosenes, naphthas, chlorinated hydrocarbons, such asperchloroethylene, and the like.

The oil phase may contain one or more primary or emulsifyingsurfactants, i.e. conventional emulsion polymerization stabilizers. Suchstabilizers are well known to the art to promote the formation andstabilization of water-in-oil emulsions. Normally such emulsifiers haveHLB values in the range of about 2 to about 10, preferably less thanabout 7. Suitable such emulsifiers include the sorbitan esters, phthalicesters, fatty acid glycerides, glycerine esters, as well as theethoxylated versions of the above and any other well-known relativelylow HLB emulsifier. Examples of such compounds include sorbitanmonooleate, the reaction product of oleic acid with isopropanolamide,hexadecyl sodium phthalate, decyl sodium phthalate, sorbitan stearate,ricinoleic acid, hydrogenated ricinoleic acid, glyceride monoester oflauric acid, glyceride monoester of stearic acid, glycerol diester ofoleic acid, glycerol triester of 12-hydroxystearic acid, glyceroltriester of ricinoleic acid, and the ethoxylated versions thereofcontaining 1 to 10 moles of ethylene oxide per mole of the basicemulsifier. Thus, any emulsifier may be utilized which will permit theformation of the initial emulsion and stabilize the emulsion during thepolymerization reaction.

These primary surfactants are used alone or in mixtures and are utilizedin amounts of not greater than about 5%, about 4%, about 3%, about 2% orabout 1% by weight of the total emulsion.

The aqueous phase generally comprises about 95 to 65% by weight of theinitial emulsion. Preferably, it comprises about 80 to 70% thereof. Inaddition to water, the aqueous phase contains the monomers beingpolymerized, generally in an amount of less than about 50%, about 15 toabout 40%, or about 22 to about 35%, by weight of the total emulsion,and generally chain transfer agents, initiators and sequesterants.Alternatively, the chain transfer agents, initiators and sequesterantsmay be added to the system after the preliminary emulsion has beenprepared. The initiator may also be added continuously during thepolymerization to control the rate of polymerization depending upon theparticular monomers used and their reactivities.

Alternatively, the initiator may be present in either the oil or theaqueous phase with the monomers being added either continuously orincrementally thereafter. All of these variations are well known in theart.

The monomers suitable for use in the preparation of the exemplarypolymers are described herein.

Any conventional chain transfer agent may be employed, such as propyleneglycol, isopropanol, 2-mercaptoethanol, sodium hypophosphite, dodecylmercaptan and thioglycolic acid. The chain transfer agent is generallypresent in an amount of about 0.1 to 10 percent by weight of the totalemulsion, though more may be used.

The initiator may be any free radical producing material well known inthe art. The preferred free radical initiators are the redox-type andthe azo-type polymerization initiators and they are generally used in anamount of about 0.0005 to 0.5 percent by weight of the total emulsion.Radiation may also be used to initiate the reaction.

Any conventional sequesterant may also be present in the aqueous phase,such as ethylenediaminetetraacetic acid or pentasodiumdiethylenetriamine pentaacetate. The sequesterant is generally presentin an amount of about 0.01 to 2 percent by weight of the total emulsion,though more may be utilized.

Following preparation of the preliminary emulsion, polymerization of themonomers is commenced at a temperature sufficiently high to break downthe initiator to produce the desired free radicals. Generally a suitabletemperature is about −20° C. to about 200° C., or about 20° C. to 100°C.

Preferably the polymerization is run at a pH of about 2 to 12 and asuitable amount of base or acid may be added to the preliminary emulsionto achieve the desired pH. The polymerization is usually completed inabout an hour or two to several days, depending upon the monomersemployed and other reaction variables. It is generally carried out atatmospheric pressure, but higher pressures are advantageously used whenvolatile ingredients are involved.

In certain exemplary embodiments, once polymerization is complete, theamount of water in the emulsion may be reduced or removed as desired.For example, the water can be removed to a level of less than about 12%,or less than about 10%, or less than about 7%, or less than about 5%, orless than about 3% by weight. In exemplary embodiments, the removal ofwater is carried out by any suitable means, for example, at reducedpressure, e.g. at a pressure of about 0.00 to about 0.5 bars, or about0.05 to about 0.25 bars. The temperature for water removal steps maytypically be from about 50° C. to about 150° C., although techniqueswhich remove water at higher temperatures may be used.

Following completion of the polymerization, the pH of the emulsion maybe adjusted as desired. For an anionic polymer emulsion, this isgenerally about 4 to 10; for cationic emulsions about 2.0 to 5.5; andfor non-ionic emulsions about 2.0 to 7.0. A breaker or invertingsurfactant, or blend of inverting surfactants, is generally added toyield a single package of final product. In exemplary embodiments, aninverting surfactant composition, as described herein, is added to thepolymer emulsion. Other suitable breaker or inverting surfactants may beused in combination with the exemplary polymer and exemplary invertingsurfactant composition in the emulsion. As described herein, the totalamount of inverting surfactants present in the emulsion is about 0.1 toabout 5% by weight, based on the total emulsion.

Once prepared, the emulsions of the present embodiments may bechemically modified in any known manner. “Chemically modified” isintended to cover further treatment of the dispersed water-solublepolymer and/or the addition of components to the dispersed water-solublepolymer which, without the stabilization provided by the emulsionstabilizers, would cause the normally water-soluble polymeric particlesto coagulate or agglomerate. Examples of such further treatments aredisclosed in U.S. Pat. Nos. 4,052,353 and 4,171,296, incorporated hereinby reference. The emulsion of the present embodiments may also beconcentrated in any suitable manner, such as is disclosed in U.S. Pat.No. 4,021,399, incorporated herein by reference.

A variety of different mixtures may be used to prepare an emulsion foruse in the present embodiments. Suitable mixtures may includeacrylamide, other monomers, water, a water-immiscible liquid, aninitiator, and an emulsifier. Generally the one or more ethoxylatedamine compounds can be combined with one or more inverting surfactantsto form the inverting surfactant composition. The inverting surfactantcomposition can be added to the polymer emulsion to form a mixture.Optionally, the mixture further may comprise, a base (e.g., sodiumhydroxide) to neutralize the monomers in acid form such that the salt ofthe monomer is not formed, a complexing agent to allow the gradualrelease of monomers in the polymerization reaction, an activator toinitiate polymerization at a lower temperature, and an inverter. Thoseof ordinary skill in the art, with the benefit of this disclosure, will,know the amount and type of components to include in the mixture basedon a variety of factors, including the desired molecular weight andcomposition of the polymer and the desired initiation temperature.

Generally, the exemplary emulsions are particularly suitable for use inbrine. The exemplary emulsions may be used in a range of temperatures,for example between about 5 and about 99° C., or about 50 and about 95°C.

In certain exemplary embodiments, the emulsion may be used incombination with a proppant.

Treatment Fluids

The treatment fluid, for example an aqueous treatment fluid, containingthe emulsions described herein, can be used in any well treatment fluid,including but not limited to stimulation, production and completionoperations. For example, the well treatment fluid can be used forhydraulic fracturing applications or in an application where frictionreduction is desired. Conventional fracturing fluids typically containnatural or synthetic water soluble polymers, which are well known in theart. Water soluble polymers viscosify the aqueous liquids at relativelylow concentrations due to their high molecular weight.

In an exemplary embodiment, the treatment fluid comprises water and anexemplary emulsion described herein. The treatment fluids may beprepared by mixing an exemplary emulsion with water. The additionalwater that is mixed with the emulsion to form the treatment fluid may befreshwater, saltwater (e.g. water containing one or more salts dissolvedtherein), brine (e.g. produced from subterranean formations), seawater,or combinations thereof. Generally, the water used may be from anysource, provided that it does not contain an excess of compounds thatmay adversely affect other components in the aqueous treatment fluid orthe formation itself. In certain exemplary embodiments, the water isbrine with a total dissolved solids content (TDS) of about 5,000 toabout 300,000 ppm, or about 100,000 to about 260,000 ppm. In certainexemplary embodiments, the total divalent cationic species content ofthe brine is in the range of about 5,000 to about 100,000 ppm, or about10,000 to about 50,000 ppm.

In exemplary embodiments, the polymer may be present in the treatmentfluid in an amount of about 0.01% to about 1% by weight of the treatmentfluid.

In these applications, the treatment fluid, can be configured as agelled fluid, such as a linear gel, a crosslinked gel, or a foamed gelfluid; acidic fluids, water and potassium chloride treatments, and thelike. The fluid is injected at a pressure effective to create one ormore fractures in the subterranean formation. Depending on the type ofwell treatment fluid utilized, various additives may also be added tothe fracturing fluid to change the physical properties of the fluid orto serve a certain beneficial function. In one embodiment, the fluiddoes not contain a sufficient amount of water soluble polymer to form agel.

In exemplary embodiments, the treatment fluid comprises a proppant.

In various exemplary embodiments, the proppants may be finely sizedsand. Generally sand is referred to by the size of mesh which the sandwill pass through, and the size of mesh which the sand will not passthrough. Typically, a 20-40 mesh sand is used but other sizes, such as40-50 or 40-60, may be utilized. Sand is also characterized by the“roundness” of the sand particles. Generally rounder sand is utilized inorder to create more uniform void spaces between the particles andtherefore better permeability within the propped fracture. Fracturingfluids also contain, for example, viscosifiers to slow the rate at whichsand will separate from the fluids and permit the sand to be carriedfarther into the fractures.

In other exemplary embodiments, other types of proppants may be used.For example, the proppant may be a ceramic proppant. The proppant may bea coated proppant, such as proppants with coatings with low coefficientsof friction in order to reduce erosion caused by the fracturing fluid.Coatings also may be used to make the sand particles more round.Examples of such coatings include antimony trioxide, bismuth, boricacid, calcium barium fluoride, copper, graphite, indium, fluoropolymers(FTFE), lead oxide, lead sulfide, molybdenum disulfide, niobiumdielenide, polytetrafluoroethylene, silver, tin, or tungsten disulfideor zinc oxide. Ceramic proppants are suggested, for example, in U.S.Pat. No. 4,555,493 to Watson et al., and low density ceramic proppantsare suggested in U.S. Pat. No. 8,420,578 to Usova et al.

Fracturing fluids may also contain other components as necessary ordesired. For example, the fracturing fluids may contain acids forbreaking the thickening polymers, salts such as calcium chlorides toincrease the density of the fluids, corrosion inhibitors or otheradditives in the fracturing fluids.

Also, fluid loss agents may be added to partially seal off the moreporous sections of the formation so that the fracturing occurs in theless porous strata. Other oilfield additives that may also be added tothe fracturing fluid include emulsion breakers, antifoams, scaleinhibitors, H₂S and or O₂ scavengers, biocides, crosslinking agents,surface tension reducers, buffers, fluorocarbon surfactants, claystabilizers, fluid loss additives, foamers, friction reducers,temperature stabilizers, diverting agents, shale and clay stabilizers,paraffin/asphaltene inhibitors, corrosion inhibitors, and acids. Forexample, an acid may be included in the aqueous treatment fluids, amongother things, for a matrix or fracture acidizing treatment. Infracturing embodiments, propping agent may be included in the aqueoustreatment fluids to prevent the fracture from closing when the hydraulicpressure is released. In a particular embodiment, the treatment fluidfurther comprises a biocide.

Methods of Use

The emulsions and treatment fluids of the present embodiments may beused in any subterranean treatment. Such subterranean treatmentsinclude, but are not limited to, drilling operations, stimulationtreatments, and completion operations. Those of ordinary skill in theart, with the benefit of this disclosure, will be able to recognize asuitable subterranean treatment. In exemplary embodiments, the emulsioncomprises: water; a water-immiscible liquid; about 10% to about 80% byweight one or more polymers; and about 0.1% to about 5% by weight anexemplary inverting surfactant composition described herein.

In exemplary embodiments, the methods may further comprise preparing thetreatment fluid, or aqueous treatment fluid. Preparing the treatmentfluid may comprise providing an emulsion as described herein, andcombining the emulsion with water to form the treatment fluid.

In exemplary embodiments, a method of treating a portion of asubterranean formation comprises: providing a treatment fluid of thepresent embodiments comprising an emulsion as described herein, andintroducing the treatment fluid into the portion of the subterraneanformation. In some embodiments, the treatment fluid may be introducedinto the portion of the subterranean formation at a rate and pressuresufficient to create or enhance one or more fractures in the portion ofthe subterranean formation. The portion of the subterranean formationthat the treatment fluid is introduced will vary dependent upon theparticular subterranean treatment. For example, the portion of thesubterranean formation may be a section of a well bore, for example, ina well bore cleanup operation. In the stimulation embodiments, theportion may be the portion of the subterranean formation to bestimulated. In exemplary embodiments, the treatment fluid may beintroduced into the portion of the subterranean formation at a rate ofabout 30 bpm to about 250 bpm, or about 50 bpm to about 175 bpm.

In exemplary embodiments, a method of treating a subterranean formationcomprises: providing a treatment fluid comprising an exemplary emulsiondescribed herein; and introducing the treatment fluid into asubterranean formation.

In exemplary embodiments, a method of fracturing a subterraneanformation comprises: (a) providing an exemplary emulsion as describedherein; (b) mixing the emulsion with additional water to form atreatment fluid, wherein the one or more polymers are present in thetreatment fluid in an amount of about 0.01% to about 1% by weight of thetreatment fluid; and (c) introducing the treatment fluid into asubterranean formation at or above a pressure sufficient to create oneor more fractures in the subterranean formation. In exemplaryembodiments, the treatment fluid comprises brine. In exemplaryembodiments, the exemplary emulsion or treatment fluid comprisesproppant. In certain exemplary embodiments, a propping agent (orproppant) such as sand or other hard material is added to the exemplaryemulsions or treatment fluids which serves to keep the fractures openafter the fracturing operation.

The fractures produced may be propped using proppants, or the fracturingfluid may include reactants to react with the surface of the rock facesto result in permeability along the fracture. The fractures may beutilized in vertical or horizontal wells, to produce natural gas, lighttight oil, or for injection of fluids into the formation.

Fracturing, or fracking, of formations is generally accomplished byinjection of a slurry of fracturing fluid and proppant into theformation at pressures sufficiently great to exceed the tensile strengthof the formation and cause the formation to separate at the point of theperforations. Formations will generally have a direction where theformation is under the least amount of stress, and the fracture willinitially propagate in a plane perpendicular to the direction of suchleast stress. In deep formations, the weight of the overburden willgenerally assure that the direction of minimal stress is a horizontaldirection. It is generally the goal to provide horizontal wellbores insuch formation in the direction of the minimal formation stress so thatfractures from the wellbore will tend to be perpendicular to thewellbore. This allows access to the maximum possible volume of formationfrom a horizontal wellbore of a limited length.

Any method for hydraulic fracturing of formations known in the art mayutilize the exemplary emulsions and treatment fluids.

Propagation of fractures is typically halted or at least inhibited byinterfaces between formations because the force exerted at the tip ofthe fracture can be dispersed at the interface of the formations. Largerfractures may therefore tend to have more rectangular shapes rather thandisk shapes as the dimensions of the fracture exceed the height of theformation, and the fracture therefore grows laterally rather thancontinuing to grow vertically.

In exemplary embodiments, methods for improving friction reductionproperties of a treatment fluid, comprising: (i) providing an exemplaryemulsion as described herein; and (ii) inverting the emulsion in thetreatment fluid comprising brine. In certain embodiments, the resultanttreatment fluid has an improvement in friction reduction, when comparedto a similar treatment fluid in which the inverted emulsion is otherthan an exemplary inverting surfactant composition as described herein.

In certain embodiments, the emulsion further comprises an emulsifier. Inone embodiment, the improved friction reduction property is the percentfriction reduction of the treatment fluid. In one embodiment, theimproved friction reduction property is the time to achieve maximumfriction reduction, or a desired percentage of the maximum frictionreduction, for example 90%. In certain exemplary embodiments, themethods described herein provide an energy savings over methods whichutilize a similar treatment fluid in which the inverted emulsion isother than an exemplary inverting surfactant composition as describedherein.

In exemplary embodiments, a method for improving friction reductionproperties of a treatment fluid comprises: (i) providing an emulsioncomprising: water; a water-immiscible liquid; one or more polymers; andan inverting surfactant composition comprising two or more surfactantsselected from the group consisting of Surfactant A compounds, SurfactantB compounds, and Surfactant C compounds; and (ii) inverting the emulsionin the treatment fluid comprising brine; wherein the resultant treatmentfluid has an improvement in friction reduction, when compared to asimilar treatment fluid in which the emulsion that does not contain aninverting surfactant composition comprising two or more surfactantsselected from the group consisting of Surfactant A compounds, SurfactantB compounds, and Surfactant C compounds.

In exemplary embodiments, a method for improving friction reductionproperties of a treatment fluid comprises: (i) providing an emulsioncomprising: water; a water-immiscible liquid; one or more polymers; andan inverting surfactant composition comprising two or more surfactantscomprising Surfactant B1 and Surfactant B2 compounds; and (ii) invertingthe emulsion in the treatment fluid comprising brine; wherein theresultant treatment fluid has an improvement in friction reduction, whencompared to a similar treatment fluid in which the emulsion that doesnot contain an inverting surfactant composition comprising two or moresurfactants comprising Surfactant B1 and Surfactant B2 compounds.

The inverting surfactant compositions, emulsions and treatment fluids ofthe present embodiments may have various uses, for example in crude oildevelopment and production from oil bearing formations that can includeprimary, secondary or tertiary (enhanced) recovery. Chemical techniques,including for example injecting surfactants (surfactant flooding) toreduce interfacial tension that prevents or inhibits oil droplets frommoving through a reservoir or injecting polymers that allow the oilpresent to more easily mobilize through a formation, can be used before,during or after implementing primary and/or secondary recoverytechniques. Such techniques can also be used for enhanced oil recovery,or to complement other enhanced oil recovery techniques.

The inverting surfactant compositions, emulsions and treatment fluids ofthe present embodiments may be used in any oil recovery technique, forexample an oil recovery technique where the reduction of friction orinterfacial tension is desired, or where mobilization of oil is desired.In exemplary embodiments, a method comprising using an invertingsurfactant composition, emulsion or treatment fluid as described hereinmay be utilized for oil recovery, including but not limited to enhancedoil recovery. In exemplary embodiments, the method comprises providing atreatment fluid comprising an emulsion comprising one or more polymersand an exemplary inverting surfactant composition described herein; andintroducing the treatment fluid into a subterranean formation; andrecovering hydrocarbons from the subterranean formation. In exemplaryembodiments, the method comprises providing an emulsion comprising oneor more polymers and an exemplary inverting surfactant compositiondescribed herein; and introducing the emulsion into a subterraneanformation; and recovering hydrocarbons from the subterranean formation.

In certain exemplary embodiments, the methods further comprise adding aproppant.

The term “brine” or “aqueous brine” as used herein refers to sea water;naturally-occurring brine; a chloride-based, bromide-based,formate-based, or acetate-based brine containing monovalent and/orpolyvalent cations or combinations thereof. Examples of suitablechloride-based brines include without limitation sodium chloride andcalcium chloride. Further without limitation, examples of suitablebromide-based brines include sodium bromide, calcium bromide, and zincbromide. In addition, examples of formate-based brines include withoutlimitation, sodium formate, potassium formate, and cesium formate.

The following examples are presented for illustrative purposes only, andare not intended to be limiting.

EXAMPLES

In these examples, the impact of exemplary inverting surfactantcompositions on inversion properties of certain polymer emulsioncompositions is evaluated by measuring the friction reductionperformance of polymer emulsions.

Materials and Methods for Examples 1 and 2:

I. Brine

Three types of brine were used in the examples (Brine 1, Brine 2, andBrine 3). The composition of each brine is provided in Table 1.

TABLE 1 Brine compositions TDS divalent TDS Na K Ca Sr Ba Fe Cl SO₄cationic total Sample (ppm) (ppm) Mg (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)(ppm) (ppm) (ppm) Brine 1 41,675 17,820 — 10,467 — — 110 34,713 19010,577 104,975 Brine 2 38,829 566 1,734 16,893 2,866 836 143 101,269 522,472 163,141 Brine 3 41,240 — 11,712 35,360 129 1,740 301 163,200 —49,242 253,682

II. Polymer Emulsions

A polyacrylamide emulsion was prepared by addition of a monomer phase toa surfactant containing oil phase with homogenization. The resultingmonomer emulsion was polymerized using free radical polymerizationchemistry in the presence of adequate agitation and cooling, whichresulted in a high molecular weight anionic polymer emulsion. Thepolymerization of acrylamide and co-monomers in an inverse emulsionresulted in a polymer emulsion containing sterically stabilized inverselattices. The average particle size of the inverse emulsions wastypically 0.7-1.5 micron. After polymerization, an inverting surfactantsystem was added to allow for rapid dilution and dissolution in water.

III. Friction Loop Testing

The friction loop is a laboratory instrument designed to simulate wellfracturing flow conditions. Fracturing in the field often requirespumping over 50 barrels per minute through a ˜4.5″ bore which results ina highly turbulent flow (Reynolds number: 500,000 to 5,000,000).Although it is not possible to achieve this kind of flow in the lab, thefriction loop designed simulates the field conditions to the maximumknown extent (Reynolds number: 120,000). The data generated by thislaboratory scale friction loop is accurate and widely accepted by theindustry. The main components of the friction loop are: pump, magneticflow meter and a differential pressure transmitter to create and monitornecessary conditions. All pipes and other components are constructedusing stainless steel 316L/304L material.

To test the friction reduction property of the polymer, the frictionloop reservoir was filled with 20L of the required brine (see abovetable for recipes of various brines). This brine was then re-circulatedthrough the friction loop at a flow rate of 24 gallons per minute acrossa five-foot section of half-inch diameter pipe (required to generate theabove mentioned Reynolds number). The baseline pressure drop wasmeasured. The exemplary emulsion containing polymer was now added (at ameasured concentration of 0.5 gallons of polymer per thousand gallons ofbrine or 0.5 GPTG) to the recirculating brine solution, where itinverted and dissolved. The degree of friction reduction (% FRt) at agiven time ‘t’ was calculated from the initial pressure drop ΔPi and thepressure drop at time t, ΔPt using the equation:

${\% \mspace{14mu} {FR}_{t}} = {\frac{{\Delta \; P_{i}} - {\Delta \; P_{t}}}{\Delta \; P_{i}} \times 100}$

Example 1

A cationic polyacrylamide emulsion with a 10 mole % charge was preparedaccording to standard emulsion procedure without any invertingsurfactants. This base emulsion was used to prepare Sample 1 and Sample2, which included the inverting surfactants as shown in Table 2.Similarly, an anionic base polyacrylamide emulsion with a 15 mole %charge was prepared without any inverting surfactants and this base wasused to prepare Sample 3 with the inverting surfactants shown in Table2. The performance parameters of friction reduction, which include theMax FR (maximum friction reduction), t₉₀ (time to 90% frictionreduction, a simple measure of inversion rate) and t_(max) (time tomaximum friction reduction) were measured in Brine 1, Brine 2 and Brine3 with different TDS at a dosage of 0.5 gptg and at 77° F.±3° F. Sample1 contained 3 wt% of the Surfactants A, B 1, B2 and C. Sample 2contained 2 wt % of Surfactants A, B1 and C. Sample 3 contained 3 wt %of Surfactants A and B 1. The results of the friction reductionexperiments are provided in Tables 2 and 3, as well as in FIGS. 1-5.

TABLE 2 Friction Reduction Performance of Polymer Emulsions withExemplary Inverting Surfactant Compositions Surfactant SurfactantSurfactant A B1 B2 Surfactant C Max FR Sample (wt %) (wt %) (wt %) (wt%) Water (%) T_(max) (s) T₉₀ (s) 1 30 30 10 30 Brine 1 61 38 22 1 30 3010 30 Brine 2 52 30 16 1 30 30 10 30 Brine 3 57 54 28 2 30 40 0 30 Brine1 58 51 31 2 30 40 0 30 Brine 2 54 90 42 2 30 40 0 30 Brine 3 55 103 503 30 70 0 0 Brine 1 60 53 32 3 30 70 0 0 Brine 2 59 54 34 3 30 70 0 0Brine 3 49 115 58

TABLE 3 Friction Reduction Performance of Polymer Emulsions withComparative Anionic or Cationic Inverting Surfactant Max FR T_(max) T₉₀Sample Water (%) (s) (s) Anionic Comparative Brine 1 53 92 48 AnionicComparative Brine 2 47 48 27 Anionic Comparative Brine 2 45 61 35Cationic Comparative Brine 1 41 366 155 Cationic Comparative Brine 2 50210 74 Cationic Comparative Brine 3 58 71 37

Example 2

A cationic polyacrylamide emulsion with a 10 mole % charge was preparedaccording to standard emulsion procedure without any invertingsurfactants. This base emulsion was used to prepare CPAM1-CPAM8 sampleswith the 3 wt % of inverting surfactant proportions as shown in Table 4.The surfactant compositions were premixed prior to addition to theemulsion. The friction reduction parameters for each sample weremeasured in Brine 1 at 77° F.±3° F. at a dosage of 0.5 gptg. The resultsare shown in FIG. 6.

TABLE 4 Friction Reduction Performance of Polymer Emulsions withExemplary Inverting Surfactant Compositions Proportion of InvertingSurfactants Sample A:B:C (wt %) Max FR (%) T_(max) (s) T₉₀ (s) CPAM120:40:40 61 41 25 CPAM2 30:40:30 58 50 28 CPAM3 0:50:50 58 45 27 CPAM40:40:60 54 50 28 CPAM5 0:100:0 54 70 44 CPAM6 0:30:70 52 83 36 CPAM730:30:40 50 169 36 CPAM8 20:30:50 50 179 38

Example 3

An anionic polyacrylamide emulsion with a 15 mole % charge was preparedaccording to standard emulsion procedure without any invertingsurfactants. This base emulsion was used to prepare APAM1-APAM5 sampleswith the 3 wt % of inverting surfactant proportions as shown in Table 5.The surfactant compositions were premixed prior to addition to theemulsion. The friction reduction parameters for each sample weremeasured in Brine 1 at 77° F.±3° F. at a dosage of 0.5 gptg. The resultsare shown in FIG. 7.

TABLE 5 Friction Reduction Performance of Polymer Emulsions withExemplary Inverting Surfactant Compositions Proportion of InvertingSurfactants A:B:C Sample (wt %) Max FR (%) T_(max) (s) T₉₀ (s) APAM130:70:0 60 53 32 APAM2 30:50:20 55 91 45 APAM3 30:40:30 53 87 50 APAM410:60:30 52 117 71 APAM5 0:60:40 50 117 73

In the preceding specification, various embodiments have been describedwith reference to the examples. It will, however, be evident thatvarious modifications and changes may be made thereto, and additionalembodiments may be implemented, without departing from the broader scopeof the exemplary embodiments as set forth in the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense.

1. An emulsion comprising: water; a water-immiscible liquid; greaterthan about 10% by weight one or more polymers; and about 0.1% to about5% by weight an inverting surfactant composition comprises one or moresurfactants selected from the group consisting of ethoxylated aminecompounds, ethoxylated fatty acid compounds, and alkylpolyethyleneglycol ether carboxylic acid compounds, alkyl polyglycolether carboxylic acid compounds, and salts or esters thereof.
 2. Theemulsion of claim 1, wherein the inverting surfactant compositioncomprises two or more surfactants selected from the group consisting ofethoxylated amine compounds, ethoxylated fatty acid compounds, and alkylpolyethyleneglycol ether carboxylic acid compounds, alkyl polyglycolether carboxylic acid compounds, and salts or esters thereof.
 3. Theemulsion of claim 1, wherein the inverting surfactant compositioncomprises three or more surfactants selected from the group consistingof ethoxylated amine compounds, ethoxylated fatty acid compounds, andalkyl polyethyleneglycol ether carboxylic acid compounds, alkylpolyglycol ether carboxylic acid compounds, and salts or esters thereof.4. The emulsion of claim 1, wherein the one or more of the polymers isan acrylamide-containing polymer.
 5. The emulsion of claim 1, whereinthe one or more polymers comprises acrylamide or partially hydrolyzedacrylamide and one or more anionic monomers.
 6. The emulsion of claim 1,wherein the one or more polymers comprises acrylamide or partiallyhydrolyzed acrylamide and one or more cationic monomers.
 7. The emulsionof claim 1, wherein the one or more polymers comprises acrylamide orpartially hydrolyzed acrylamide and one or more monomers selected fromthe group consisting of acrylic acid and salts thereof
 8. The emulsionof claim 1, wherein the one or more polymers comprises acrylamide orpartially hydrolyzed acrylamide, and acryloyloxyethyltrimethylammoniumchloride.
 9. The emulsion of claim 1, wherein the ethoxylated aminecompound is polyoxyethylene tallow amine.
 10. The emulsion of claim 1,wherein the alkyl polyethyleneglycol ether carboxylic acid compounds isglycolic acid ethoxylate oleyl ether.
 11. The emulsion of claim 1,wherein the ethoxylated fatty acid compound is ethoxylated castor oil.12. The emulsion of claim 1, wherein the alkyl polyglycol ethercarboxylic acid compound is polyoxyethylene lauryl ether carboxylicacid.
 13. The emulsion of claim 1, wherein the inverting surfactantcomposition comprises one or more surfactants selected from the groupconsisting of alkyl polyethyleneglycol ether carboxylic acid compounds,alkyl polyglycol ether carboxylic acid compounds, and salts or estersthereof
 14. The emulsion of claim 2, wherein the inverting surfactantcomposition comprises about 5 to about 95 wt % one or more ethoxylatedamine compounds, and about 5 to about 95 wt % one or more alkylpolyethyleneglycol ether carboxylic acid compounds, alkyl polyglycolether carboxylic acid compounds, and salts or esters thereof.
 15. Theemulsion of claim 2, wherein the inverting surfactant compositioncomprises about 5 to about 95 wt % one or more ethoxylated aminecompounds, and about 5 to about 75 wt % one or more ethoxylated fattyacid compounds.
 16. The emulsion of claim 2, wherein the invertingsurfactant composition comprises or consists essentially of about 5 toabout 95 wt % one or more alkyl polyethyleneglycol ether carboxylic acidcompounds, alkyl polyglycol ether carboxylic acid compounds, and saltsor esters thereof and about 5 to about 75 wt % one or more ethoxylatedfatty acid compounds.
 17. The emulsion of claim 2, wherein the invertingsurfactant composition comprises about 5 to about 95 wt % one or morealkyl polyethyleneglycol ether carboxylic acid compounds, alkylpolyglycol ether carboxylic acid compounds, and salts or esters thereof,and about 5 to about 95 wt % a different alkyl polyethyleneglycol ethercarboxylic acid compounds, alkyl polyglycol ether carboxylic acidcompounds, and salts or esters thereof.
 18. The emulsion of claim 3,wherein the inverting surfactant composition comprises about 5 to about90 wt % one or more ethoxylated amine compounds; about 5 to about 90 wt% one or more alkyl polyethyleneglycol ether carboxylic acid compounds,alkyl polyglycol ether carboxylic acid compounds, and salts or estersthereof; and about 5 to about 75 wt % one or more ethoxylated fatty acidcompounds.
 19. A treatment fluid comprising an emulsion of claim 1, andadditional water; wherein the one or more polymers are present in thetreatment fluid in an amount of about 0.01% to about 1% by weight of thetreatment fluid.
 20. The treatment fluid of claim 19, further comprisinga proppant.
 21. A method of treating a subterranean formation,comprising: providing a treatment fluid comprising an emulsion of claim1; and introducing the treatment fluid into a subterranean formation.22. A method of fracturing a subterranean formation, comprising: (i)providing an emulsion of claim 1; (ii) mixing the emulsion withadditional water or brine to form a treatment fluid, wherein the one ormore polymers are present in the treatment fluid in an amount of about0.01% to about 1% by weight of the treatment fluid; and (iii)introducing the treatment fluid into a subterranean formation at orabove a pressure sufficient to create one or more fractures in thesubterranean formation.
 23. The method of claim 21, wherein thetreatment fluid comprises brine.
 24. The method of claim 21, furthercomprising adding a proppant.